Fluid system automatic vent valve



June 1, 1948. .1. HULMAN 2,442,361

FLUID SYSTEM AUTOMATIC VENT VALVE Filed Sept. 4, 1944 I 5 it;

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j /zd-VZZ 00 W 3 `32 Patented Je M1948 TATES PATENT OFFICE.

(Granted under the act oi March 3, 1883, as amended April 30. 192.8; 370 0. G. '157) 3 Claims.

The invention described herein may be manufactured and used by or for the Government for governmental purposes, without the payment to me of any royalty thereon.

This invention relates to uld pressure systems. of that class in which a fluid is required to be maintained under a substantially constant pressure by a pumping or similar means, and more particularly to a means for separating air or vapor from the oil or other liquid which is being pumped.

In systems of this character, particularly wherein the pump oi the system has its suction or low pressure side connected to a supply tank or reservoir from which it takes liuid and discharges it into the high pressure side of the system, it happens `frequently and for various reasons that air or vapor gets into the liquid l and the system becomes air or vapor locked. If

the amount of air or vapor is minute, the pump may discharge it into the high pressure side, which will of course cause the pressure in the high pressure side to drop but not enough-to result seriously. However, if the volume of air or vapor entering the pump is larger, the pump may lose its prime. Moreover, if the system is one o that type wherein a plurality of pumps are connected in parallel, and are provided with check valves biased to prevent return of uid from an operative pump backward through a disabled pump, a pump which has lost its prime will not regain it, in which case the unprimed pump may be permanently disabled, particularly if the liquid in the system is depended on for lubrication of the pumps.

It is therefore an object of this invention to provide, in a system of this kind, asimple, inexpensive and effective means to arrest air or vapor coming through the pump from the suction side to the discharge side, and return it to the vented interior of the supply reservoir without passing it into or through the high pressure side of the system.

More specifically stated it is an object of the invention to retain the conventional check valve, which is usually placed between the discharge side of the pump and the remainder of the high pressure side of the system to prevent the return of the uid under pressure through the pump, but supplement this conventional check valve with a vent valve which opens in response to a drop in pressure at the upstream side of the check valve caused by air or vapor being pumped from the suction to the discharge side.

Other objects and advantages will become evident from the following detailed description when considered with reference to the drawing, wherein:

Fig. 1 is a longitudinal axial sectional view through the improved valve structure which is adapted to be connected to, or to extend integrally from the discharge side of the iuid pump of the system, the vent valve being shown in the closed position.

Fig. 2 is a longitudinal axial section through the vent valve when it is in the open position.

Fig. 3 is an end view of the device shown in Fig.

Fig. 4 is a longitudinal axial section through a modified form of vent valve.

Fig. 5 shows a further modiiication of the vent va ve.

In the drawing, a valve body lli which normally houses only a check valve I2 is here provided with a bulge I4 to contain also the vent valve i6.

The check valve I2 comprises a triangular valve head I8 beveled at 20 for engagement with the valve seat 22 at the right hand end of the main iluid conduit 23, and having the three points 24 oi the triangle slidable freely in a bore 26 ofy the body I0. A spring 28 is biased to hold the head I8 on the seat 22, the spring being held under an initial stress by a threaded plug 30 which is provided with a series of holes 32 through which fluid. coming through the valve l2 may pass.

The vent valve i6 comprises a casing 34 which is snugly fitted to la bore 36 in the bulge i4. A part 38 of the casing 34 is externally threaded to fit into corresponding internal threads in the housing il), whereby the casing is held in place in the housing. Seal rings 40 prevent leakage of fluid between the casing 34 and the bore 36.

The casing 34 is provided with a bore 42 within which a small piston 4 4 is axially slidable. The bore 42 is open at the right end and closed at the left as shown. A spacing tube 46 is provided to limit movement of the piston 44 to the left while the end wall of the bore 3S 4limits its movement to the right. A light spring 48 surrounding the tube 4B is just sufficient to hold the piston 44 to the right end of its travel as shown in Fig. 1 except when the vent valve becomes active to eliminate air or vapor in which case it moves to the position shown in Fig. 2.

A passageway 50 connects the main passageway 23 to an annular groove 52 surrounding the casing 34, and several small holes 54 connect the groove 52 to the space between the coils/of the spring 48. Several small holes I8 pass through the wall 62 which surrounds the piston. Several radial f holes 64 connect the annular groove 82 to an annular groove 68 which surrounds the casing 34. A vent opening 68 communicates with the groove 68 and is threaded as at 10 for pipe-con nection to the vented top oi' the uid reservoir oi' the system. A passageway Y12 connects the bore 42 of the casing 84 to an internal annular groove 14 in the bore 26 whereby the right hand end of the piston 44 is at all times exposed to the pressure in the space 16 which is a part of the high pressure side of the system.

The operation of the device shown in Figs. 1,

2, and 3 is as follow:

During normal operation of the system, uid ilows from the discharge side of the pump of the system through the conduit 28 and valve I2 into the chamber 16 and into the piping or containers which constitutes the high pressure side of the system. There will be a slight pressure drop from the conduit 23 to the chamber 16, the amount of drop depending mainly on the strength of the spring 28. Since the pressure in conduit 23 acting through the passageway 50 exceeds the pressure of chamber 16 acting through passageway 12, the normal tendency of the piston 44 is to move to the right. This tendency is slightly augmented by the light spring 48 if this spring is used. It is noted, however, that while use of the spring 48 is desirable, it may be eliminated without seriously aecting the operation oi.' the device. As long, therefore, as no air or vapor comes from the discharge side o! the pump into the conduit 23, the device will remain in the condition shown in Fig. 1.

If. however. any substantial volume of air or vapor is discharged by the pump into the conduit 23, a sharp pressure drop in the conduit 23 will take place, because of the fact that the air or vapor requires a great reduction in volume and therefore considerable pumping eiiort to raise the pressure of the air or vapor to that of the liquid in the chamber 18. Y

When then, due to air or vapor being brought into the conduit 23, the pressure in conduit 23 drops far enough below that in the chamber 16 to slightly more than balance the effort of the light spring 48 or to overcome the friction of the piston 44 in its bore, if the liglt spring 48 is not used, the piston 44 will move to the left as in Fig. 2 and the airv or a'lpor will pass through the passageways 50, 52, 54, 56, 58, 60, 62, 64, 66, and 88 back to the vented top of the supply reservoirs from which fluid is being pumped.

With the air or vapor thus eliminated, the pressure will rise rapidly in the conduit -23, and, as soon as this pressure, plus the effort of the spring 48, if used, exceeds the pressure, in the chamber 16,'the piston 44 will return to the normal position shown in Fig. 1 where the vent valve I8 is closed.

As a more concrete example of the operation of the device oi' Figs. 1, 2 and 3, let it be assumed that an unloading valve or relief valve downstream of the check valve I2 is set to maintain a pressure in the chamber 16 of 1000 lbs.; that the check valve spring 28 is under a stress of 10 lbs. in which case the pump being used must have capacity to raise the pressure in conduit 23 1.59

4 slightly over 1010 lbs., and that the light spring 48 is under a stress of 21bs.

If a sui'iiciently large volume of air or vaporr now enters the conduit 23. the pressure in conduit 23 may drop as low as 500 lbs. When this happens, the 1000 lb. pressure in chamber 14 will moveA the piston 44 to the left, asin Fig. 2, thus opening the vent passage 80.

As the pump continues to operate, the air will rst be discharged through the vent 60-08, or. if the air is admixed with the hydraulic uid. the mixture will pass through the vent opening 60. It should at this point be noted that the vent 60, or some other part of the channel through which the air must pass, must be of such size, with respect to the capacity of the pump that, as long as air, or mixed hydraulic iiuid and air is passing out the vent 60 the pump can not build up pressure in the conduit 23. great enough to close the vent valve, but when the air or mixture has all been discharged, and the pump is again pumping the heavier medium. the pump can build up pressure in the conduit 23 suillcient to close the vent valve in spite of the leakage through the vent 60.

When the pressure in the chamber 23 is thus built up to 999 lbs., this pressure, plus the 2 lb. stress of the spring 48, if the spring 48 is used, making 1001 lbs. pressure urging the piston 44 to the right, and since the pressure in the chamber 'I6 is only 1000 lbs. the piston 44 moves to the right and closes the vent 60.

Since the pressure in conduit 23 is now only 999 lbs. and the pressure in chamber 16 plus the spring 28 is 1010 lbs. the check valve is still closed. but several additional seconds operation of the pump will make up this deilciency and the check valve I2 will open and the system be back to normal.L

In the modification shown in Fig. 4, the bulge I4 is bored as at 18 and provided at the closed end of the bore with an inserted valve cage l0. the outer end of the bore being closed by a screw plug 8,2.

The valve head 84 has a seat 88 in the cage 8| and an integral stem 88 which is slidable in a bearing 90 in the cage. An annular space 9| surrounds the stem 88 near one end and an annular chamber 93 surrounds the stem near the other end. The space 9| may be connected by a groove 95 to the chamber 93 and the chamber 93 to the atmosphere through the opening 48, or the groove 95 may be omitted if the bearing 90 is slightly loose on the stem 88. A diaphragm 92 has its central portion secured to the stem 88 by a nut 94 and its perimeter secured tothe cage 80 by a hollow externally screw-threaded plug 96. A light compression spring 98 may be held under an initial 'stress between the plug 82 and the valve head 84 in the chamber |00, or the spring may be omitted and the pressure in tle chamber |00 relied upon to close the valve. As long as the pressure entering the chamber |60 at 50, plus the pressure of the small spring 98, if used, is greater than the pressure entering at 12 and acting on the diaphragm 82, the valve head 84 will remain on its seat 88. The entry of an amount of air or vapor that will cause the pressure to drop to an extent where the pressure in the chamber |00 plus the pressure of the light spring 98 is less than the pressure entering at 12, will cause the valve head 84 to rise from its seat 86 and permit the air to escape through thevent 68.

In the modification shown in Fig. 5, the bulge lI4 is fitted with a casing 11, the bore of which is stepped, having a larger portion 19 and a smaller portion 8i to which a stepped piston 83 is slidably tted. With the exception of being stepped, the piston 83 is like that shown in Fig. 1, having an axial opening 58, transverse openings 60, the annular groove 62, the vent opening 68 and the threaded portion 10. Additionally the space 85 adjacent the step in the piston is carried through a passageway 81 to the vent (iB-10. A spring 89 urges the stepped piston toward the right to the closedvent position shown.

With the left end of the piston 83 having a greater area exposed to pressure than the right end, it is obvious that the valve will shift to the closed position shown when the pressure on the left or upstream side 0f the piston is still much below that of the downstream side. Under this condition, the vent passages 58,V 60, 68, etc., must be of such size or be so restricted that the air or mixture of oil and air will all have passed out through the vents before the pumped pressure shifts the valve. Thereafter a relatively short period of additional pumping into the passageway 23 will be required to reach a pressure which will open the valve i8, the period depending, of course, on the amount of step in the piston 83.

While in the several exemplications of the invention shown, springs are used in both the check valve and the vent valve for urging them to the closed positions, it is obvious that the springs in both cases may be omitted and the valves be closed by the pressure alone, since the pressure in the conduit 23 exceeds that in the chamber 16 when no air or vapor is present in the conduit 23, whereas the pressure in the chamber 18 exceeds that in the conduit 23 where air or vapor enters the conduit.

It is further noted that in both examples shown the vent valve is made as a separate unit and inserted into the main valve body l0, it is obvious, however, that the vent valve casing 3B or valve cage 80 could be made an integral part of the body I0.

Having described several embodiments of my invention in which the objects set forth are attained. I claim:

1. A valve mechanism comprising a body having a flow passage therethrough with upstream and downstream ends adapted respectively to receive and discharge a hydraulic fluid -under pressure, a check valve in said flow passage intermediate said ends biased to prevent flow from said downstream and back to said upstream end, an opening connecting the ow passage upstream of the check valve back to the flow passage downstream of the check valve, said opening including a cylindrical portion, an air vent in the wall of said cylindrical portion, a piston in said cylindrical portion slidable downstream in said cylindrical portion to a vent closing position when the pressure in the upstream end exceeds the pressure in the downstream end and slidable upstream in said cylindrical portion to a vent opening position when the pressure in the upstream end falls below the pressure in the downstream end, a spring urging said check valve to the closed position, whereby the pressure in the upstream end normally exceeds the pressure in the downstream end, the upstream end of said piston having at least as large an area as the downstream end, whereby the pressure in the upstream end must fall below the pressure in the downstream end before the vent valve can open.

2. The device of claim l in which the upstream end of the piston has a larger area than the downstream end.

3. The device dened in claim l in which there is a second spring urging the piston toward the downstream end, and in which the force of said second spring taken together with the force of the pressure acting on the upstream end of the piston normally exceeds the .force of the pressure acting on the downstream end of the piston, whereby the vent is opened only when the upstream pressure falls below the downstream pressure.

JULIUS HULMAN.

REFERENCES CITED The following references areof record in the me of this patent:

FOREIGN PATENT 

